The present invention relates to an apparatus for removing dust accretions from a suspension smelting furnace used in the smelting of sulfidic raw materials, such as ores or concentrates, containing useful metals, such as copper, nickel or lead.
In order to recover metals, such as copper, nickel or lead, from sulfidic raw materials containing said materials, for instance from ores or concentrates, there is generally applied the suspension smelting method, where the heat amounts contained by finely divided sulfidic raw materials are made use of. In addition to sulfidic raw materials, into the reaction space of the suspension smelting furnace there is fed oxygen-containing gas, such as air, oxygen-enriched air or oxygen. In addition, to the reaction space there is fed for instance flue dust recovered and recirculated from the exhaust gases of the suspension smelting furnace, as well as metallurgic slag-forming agent, flux. In the reaction space of the suspension smelting furnace, the solid and gaseous feed materials react with each other, so that in the bottom part of the suspension smelting furnace, there are formed at least two molten phases, a slag phase and a matte phase contained by the metal to be utilized. The molten phases that are formed in the bottom part of the suspension smelting furnace, i.e. in the settler, are removed from the suspension smelting furnace at regular intervals. The sulfur dioxide bearing process gases created in the reaction space of the suspension smelting furnace are conducted, via the settler, to the uptake shaft of the suspension smelting furnace, and from the uptake shaft further to a waste heat boiler connected to the suspension smelting furnace, where the exhaust gases from the suspension smelting furnace are cooled, and at the same time the solids, i.e. flue dust, contained by the gas are removed.
When the suspension smelting furnace exhaust gases are transferred from the uptake shaft of the suspension smelting furnace to the waste heat boiler, the flowing direction of the gases is changed from an essentially vertical direction to an essentially horizontal direction. Moreover, when the flowing area of the connecting aperture between the uptake shaft and the waste heat boiler is made essentially smaller than that of the uptake shaft in order to reduce the heat losses from the suspension smelting furnace, contacts of sulfur dioxide bearing exhaust gases with the walls of the suspension smelting furnace cannot be avoided. Further, because the temperature of the exhaust gases is dropped towards the top part of the uptake shaft of the suspension smelting furnace, the molten particles contained in the exhaust gases start to be solidified, and when touching the uptake shaft walls, they are attached to the wall, particularly in the vicinity of the connecting aperture between the uptake shaft and the waste heat boiler. Thus, in the vicinity of the connecting aperture, there are accumulated dust accretions that obstruct the flowing of the exhaust gases and must therefore be broken apart.
It is an object of the invention to achieve an improved apparatus for breaking up dust accretions created in the vicinity of the connecting point between the uptake shaft and successive waste heat boiler, in the inner parts of the uptake shaft and/or the waste heat boiler, so that the dust accretions do not essentially obstruct the flowing of the exhaust gases from the uptake shaft to the waste heat boiler.
According to the invention, in the vicinity of the connecting point between the uptake shaft of a suspension smelting furnace and the waste heat boiler connected to the uptake shaft, there is installed at least one apparatus, whereby the dust accretions created in the vicinity of the connecting aperture of the uptake shaft and the waste heat boiler can be subjected to an impact effect in order to break up the dust accretions and to drop them back to the bottom part of the uptake shaft of the suspension smelting furnace and/or to the bottom part of the waste heat boiler. The apparatus according to the invention is attached to the wall of the suspension smelting furnace and/or of the waste heat boiler, so that the impact effect achieved by means of the apparatus can be conducted, through the wall of the suspension smelting furnace uptake shaft and/or of the waste heat boiler to at least one dust accretion located inside the uptake shaft and/or waste heat boiler.
In order to break up dust accretions from the inside of the suspension smelting furnace uptake shaft and/or the waste heat boiler, in the vicinity of the connecting point between the suspension smelting furnace uptake shaft and the waste heat boiler, by means of an apparatus according to the invention, in the wall of the uptake shaft and/or the waste heat boiler, on the outer wall surface, in a location corresponding to the spot where the dust accretions are accumulated, there is installed at least one striker device. By means of the striker device, strokes are directed through the wall to the counterpart of the striker device that serves as an anvil. In that end of the counterpart of the striker device, installed through the wall, that is placed inside the uptake shaft and/or the waste heat boiler, which end at the same time is the opposite end with respect to the striker device, there is further installed a striker element whereby a mechanical contact can be achieved between the striker element and the dust accretions to be broken up. The force of the stroke hit by the striker element makes the dust accretions to be broken up and detached from the wall of the uptake shaft and/or the waste heat boiler, so that they are dropped down, to the bottom part of the uptake shaft on the uptake shaft side, and to the bottom part of the waste heat boiler on the waste heat boiler side.
Advantageously the striker device meant for breaking up dust accretions operates pneumatically, hydraulically or in some other advantageous manner. The striker device may advantageously be arranged to operate so that it hits the striker counterpart, serving as the anvil, at essentially regular intervals. Naturally the striker device can also be arranged to operate so that strokes are placed only in cycles, at essentially regular intervals, or so that single strokes are hit according to the need for breaking up the dust accretions, with respect to their degree of accumulation. In addition, the impact force of the striker device provided in the apparatus according to the invention can advantageously be adjusted, in which case the hardness and adhesion caused by the composition of the dust accretions can be taken into account.